Yeah, I've looked into electrosmash. their fx pedals are guitar oriented and therefore aren't designed with the lower frequencies in mind. And based on my understanding of the boards and how they work; I don't believe It allows just a tweak of the signal.

I'm not too familiar with fx's for bass pedals but the basic idea is the same for both guitar and bass: use an ADC to capture the audio signal, then use software to manipulate it in some fashion, then use a DAC to generate new audio sound based on the manipulated audio.

Using an audio codec with something like guitarix should do the job if you can find the sort of bass fx you want